Research on the Decline of the Sediment Load in the Mississippi River Passing through Louisiana
I have repeatedly written about the role of dams, locks and reservoirs in the Mississippi River system and their role in the loss of coastal wetlands in Louisiana. Now, I will provide some research in support of this position.
Dr. Richard H. Kessel, a professor of Geography and Anthropology at Louisiana State University, is the person that has written the most extensively on the decline of the sediment load in the Mississippi River and its role in the loss of coastal wetlands in Louisiana. His papers have included:
1. An Approximation of the Sediment Budget of the Lower Mississippi River Prior to Major Human Modification which was published in volume 17, pages 711-722 (1992) of Earth Surface Processes and Landforms.
2. The Role of the Mississippi River in Wetland Loss in Southeastern Louisiana, U.S.A. which was published in Volume 13, Number 3, pages 183-193 of Environmental Geology and Water Science.
3. The Decline in the Suspended Load of the Lower Mississippi River and its Influence on Adjacent Wetlands which was published in Volume 11, Number 3, pages 271-281 of Environmental Geology and Water Science.
4. Chapter 12 Historical Sediment Discharge Trends for the Lower Mississippi River in Volume II: Technical Narrative of the Outer Continental Shelf Study by the Mineral Management Service, study number 87-0120 which larger document is entitled Causes of Wetland Loss in the Coastal Central Gulf of Mexico.
The gist of Dr. Kessel's research shows that the suspended sediment load in the Mississippi River as it passes through Louisiana has declined by about 80% since the 1850's. He divides the history of this decline into three periods. These periods are 1) Prior to 1900, 2) a pre-dam period until extensive dam construction began between 1930 and 1952, and 3) the post dam period since 1952. The suspended load decreased 41% before dam construction began and another 51 percent after the dams in the Missouri and Arkansas Rivers were constructed. This change has altered the balance between sediment deposit in the wetlands adjacent to the Mississippi River and the ongoing process of subsidence and global sea level rise. In the most recent period, the rate of sea level rise and subsidence exceeds the rate of sediment deposit. Thus, the coastal wetlands are being lost to open water.
Erich P. Rapp
